Alloy



Patented Aug. 16, 1938 UNITED STATES 2,126,; ALLOY Anthony G. de Golyer,New York, N. Y.

No Drawing 3 Claims.

The present invention relates to a new and useful alloy and relatesparticularly to an alloy containing boron, tungsten, vanadium, zirconiumand cobalt, which is characterized by being responsive to thermaltreatment for the improvement of physical properties.

An object of the present invention is to provide an alloy especiallyadapted for use as metal cut ting tools, the cutting efliciency of whichis superior to that of present known high speed steels and other alloys.A further object is to provide analloy which is free from,.orsubstantially free from carbon and which is readily amenable to thermaltreatment, by means of which the hardness, tensile strength, cuttingefficiency and other physical properties and characteristics may beaccurately controlled over a comparatively wide range.

I have found through e p riment that by alloying or otherwise intimatelycombining boron, tungsten, vanadium, zirconium and cobalt within therange of boron 0.50% to 3%, tungsten 5% to 30%, vanadium 1% to 8%,zirconium 0.25% to 5%, and cobalt substantially the balance, that Iobtain metallic compositions which possess in combination materiallyimproved physical properties compared to those of heretofore knownalloys or compositions intended for the cutting have been subjected tosuch treatment are particularly valuable for use as tools, dies and thelike for the cutting or mechanical working of metals.

Numerous metallic compositions have-heretofore been proposed asimprovement on the generally known 18-4-1 type of tungsten-chromiumvanadium high speed tool steel, and while many suchcompositions possessgreater hardness than such steel, all of them have disadvantages whichrender them unsuitable for "general application as metal cutting orforming tools. Compositions containing principally carbides of tungsten,molybdenum or tantalum bonded with a relatively soft matrix metal have ahigh degree of hardness, but are extremely brittle. 'Cast compositionsof the types heretofore proposed require the presence of at least 1.50%carbon to qualify as metal cutting tools and, as is well -known,"suchalloys Application August 25,1936, Serial No. 97,742

are not only brittle, but are so sensitive to various operatingconditions as to greatly restrict the scope of usefulness. One of thegreatest disad-- vantages of such heretofore proposed compositions'isthat none of them are responsive to ther- I mal treatment for regulationof physical properties, and consequently physical properties andcharacteristics are governed entirely by the chemical composition of thesinteredor cast material.

I My alloy may be used in the as-cast condition, or it may be forged orotherwise mechanically worked. In either caseI .prefer to subject thealloy to thermal treatment before using it as a cutting tool or die.Both the cast and forged material are equally amenable to thermaltreatment. For example, cast bodies of this alloy may have a hardness offrom 50 to on the Rockwell C. scale-and by subjecting the material tosuitable thermal treatment, such'as quenching from a temperature higherthan. approximately 1000 0., the hardness may be lowered to an'approximate range of from 40 to 47 Rockwell C. In this condition thebodies may be ground, shaped or formed, as desired. The alloy maysubsequently be submitted to a second thermal treatment, such as heatingto a temperature of less than 1000 C. for a period of one hour or more,by which the hardness may be increased to from approximately 60 toRockwell C. In the latter condition the alloy is especially valuable forthe cutting or mechanical working of a large number of metals andalloys, as well as numerous nonmetallic materials. An important propertyof this alloy is that virtually all of the maximum hardness, developedby thermal treatment, is retained when the alloy is subjected toelevated temperatures, e. g. such as are generated in the tip .ofa toolcutting metal at high speed. Although the alloy hasa high degree ofhardness and resistance to abrasion by hot metal chips, especially afterthermal treatment, it-is remarkably resistant to failure from sudden orrepeated shock. Therefore, tools made of the present alloy retain anefficient cutting edge for longer periods than other tools.

The more important distinctive and valuable advantages are, apparently,due to the presence of appreciable amounts of boron in the composition,in conjunction with the other essential component elements within thepercentages specified herein.

I have found that molybdenum may be used to supplant all or a portion ofthe tungsten of I the present alloy. Likewise, uranium may be used inplace or either tungsten or molybdenum.

Specific examples of compositions within the scope of the presentinvention which I have found well adapted for metal cutting tools, diesand the like are the following: boron 1.20%, tungsten 14%, vanadium2.75%, zirconium 1.25%, cobalt balance; boron 2.10%, tungsten 19.50%,vanadium 4%, zirconium 0.80%, cobalt balance; boron 1.65%, molybdenum13%, vanadium 3.5%, zirconium 3.75%, cobalt balance; boron 1.70%.tungsten 5%,- molybdenum vanadium 5%. zirconium 4.60%, cobalt balance;boron 1.10%, molybdenum 12%, vanadium 6%, zirconium 1.75%, cobaltbalance.

An objective of the present invention is to provide alloys having highhardness, high resistance to shock and impact, advantageous cuttingproperties for metal, etc., which are free or substantially free fromcarbon, and thus eliminate all of the serious disadvantages associatedwith carbon containing non-ferrous alloys or compositions intended formetal cutting tools. Although I'prefer to have the alloys of thisinvention entirely free from carbon, in many instances I have foundcarbon present in the nature of an impurity incidental to manufacture.It is important to restrict the amount of carbon so present to a maximumof about 0.15%, as I have found that the presence of higher percentagesof this element make the alloy extremely brittle and subject to failureduring cutting operations, and, greatly retards or entirely prevents thedesired and necessary reactions during thermal treatment. Furthermore,the presence of appreciable amounts of carbon decreases the red hardnessof the alloy, i. e. hardness at temperatures of approximately 550 C. andhigher.

By reason of the fact that the elements forming the essential componentsof the alloy of the present invention invariably are contaminated withother elements when produced in commercial quantities, the alloys of myinvention usually contain insignificant amounts of one or more elementsin the nature of impurities incidental to manufacture. Because of thefact that the maximum values of physical properties of the present alloycan be developed only through thermal treatment, it is essential thatthe amount of such incidental impurities present be limited topercentages which will not be efiective in retarding, or entirelypreventing the necessary physical reactions during thermal treatment.Further,

' the percentages of such impurities should also be restricted toamounts which will not be effective on the physical properties orcharacteristics of the alloy either before or after thermal treatment.

I have found that the most harmful impurities commonly present, inaddition to carbon, are silicon and aluminum. The presence of either ofthese elements in amounts greater than approximately 1% renders thealloy of the present invention entirely unsuitable for thermal treatmentby means of which the hardness, tensile strength and impact resistanceand other properties may be accurately controlled. One of the chiefdisadvantages of silicon and aluminum is that these elements apparentlyform chemical compounds with one or more of the essential components ofthe present alloy, and such compounds are not only hard, brittle andlacking in impact resistance, but are virtually insoluble in bon,silicon and aluminum, materially change the character of the alloythrough rendering it not amenable to thermaltreatment.

My investigations indicate that the preferred structure of a body of thepresent alloy is produced only by means of thermal treatment, and thatthis comprises at least two principal constituents: one, a relativelyhard intermetallic compound of boron with one or more of the otheressential components; and, second, a solid solution of two or more ofthe essential components which has a lower degree of hardness andfunctions as a matrix. In some instances the structure will contain athird constituent in the nature of an eutectoid. The ratio of theconstituents and the ratio of particle size in any particular body ofthe alloy maybe accurately controlled and fixed over a wide range bymeans of thermal treatment, or mechanical working and subsequent thermaltreatment.

By reason of the combined advantageous physical properties possessed bythe alloy of the present invention, tools and other articles composed ofthis alloy may be operated efliciently and economically under conditionswhich are impossible .or uneconomical with tools or articles composed ofheretofore known alloys or metallic compositions.

By the term the balance substantially cobalt in the foregoing and in thefollowing claims, I intend that the alloy of the present inventioncomprises boron, vanadium, zirconium, and metal'of the group tungsten,molybdenum and uranium, within the percentage limits specified, with theremainder cobalt except for ineffective amounts of impurities which maybe present incidental to manufacture, as hereinbefore explained.

I claim:

1. A precipitation hardened alloy containing boron 0.50% to 3%, metalfrom the group tungsten, molybdenum and uranium 5% to 30%, vanadium 1%to 8%, zirconium 0.25% to 5%, the balance cobalt.

2. A precipitation hardened alloy containing boron 0.50% to 3%, tungsten5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%, the balance cobalt.

3. A precipitation hardened alloy containing boron 0.50% to- 3%,molybdenum 5% to 30%, vanadium 1% to 8%, zirconium 0.25% to 5%, thebalance cobalt.

ANTHONY G. DE GOLYER.

